As long as it is an ultraviolet-visible spectrophotometer, it must have an electro-optical system (a light-emitting bulb that has a very stable power supply that matches the lamp). An ultraviolet visible spectrophotometer in the electro-optical system, as long as the light or power of any one of the two problems (failure), it will seriously affect the stability of the instrument or other performance specifications. Winstead's research practice has long pointed out: 90% of the spectral instrument is unstable, due to power instability caused by. For example, the UV-visible spectrophotometer light source, generally there are two kinds of deuterium lamp, tungsten lamp, we both require a good light bulb, but also requires the lamp power supply is stable; if the light bulb itself is not good (such as heat caused by drift, deuterium lamp life expires After the launch of the luminous flux of less than 50%, tungsten lamp life expired or filament is not correct or shiny surface contamination and other defects, etc.), certainly the machine will not be stable, the machine's other performance specifications will be affected, At this time, it is impossible to develop or produce high-quality outside the visible spectrophotometer, can not be accurate and reliable analysis of test data; if the bulb is very good, Sa its light supply power supply instability, certainly the machine will not be stable, It is impossible to develop or produce high-quality UV-visible spectrophotometer, it is impossible to get accurate and reliable analysis of test data. Scientists from the theory of instrumentation theory of electronics and electro-optical devices related to the theory of light bulb issued by the luminous flux stability, and the stability of the power supply to the bulb was studied. The results show that if the current of the constant current power supply of the deuterium lamp fluctuates by 1%, the luminous flux emitted by the deuterium lamp fluctuates by 6.7%. This fluctuating data can be verified by theoretical calculations; since the working current of the general deuterium lamp is 300mA and the current fluctuates by 1% or 3mA, the luminous flux fluctuation value can be calculated. It can be seen, the electro-optical system, the importance of light bulbs and power is self-evident.